Bazinga! “The Big Bang Theory” is celebrating a huge milestone Thursday night with the premiere of its 200th episode. To honor the event, the hit CBS sitcom is throwing Sheldon (Jim Parsons) a birthday party — a first for the series. Of course, Sheldon has some bizarre demands. But members of the gang have some special surprises up their sleeves for their good friend — like the guest appearance of “Batman” star Adam West!
The 87-year-old actor, along with some other celebrities, will swing by Sheldon and Leonard’s (Johnny Galecki) Pasadena apartment to wish the superhero fan a very happy birthday. To honor the event, we’re looking back at every single guest star who has appeared on “The Big Bang Theory” in the course of the show’s nine seasons:
DJ Qualls (Season 1, episode 10)
Before appearing on “Z Nation” and “The Man in the High Castle,” DJ Qualls appeared as a research assistant. Sheldon enlists his help to get out of going to see Penny perform “Rent.”
Charlie Sheen (Season 2, episode 4)
Back when Charlie Sheen was still on creator Chuck Lorre’s good side, he briefly appeared as himself on “Big Bang Theory.” He turns around when Raj brags about being in People magazine.
Octavia Spencer (Season 2, episode 5)
“Mom” actress Octavia Spencer guest starred as a DMV employee who has to deal with Sheldon in “The Euclid Alternative.”
Michael Trucco (Season 2, episode 11)
“Battlestar Galactica” alum Michael Trucco guest starred as Dr. David Underhill, a new addition to the Physics department at Cal Tech. While Leonard is initially happy to work with him, his attitude changes when Dr. Underhill begins to date Penny.
Lewis Black (Season 3, episode 2)
Sheldon, Howard and Raj go to Professor “Creepy” Crawley, played by comedian Lewis Black, to figure out what kind of cricket they caught. But Professor “Creepy” Crawley has his own issues to deal with.
Wil Wheaton (Season 3, episode 5)
“Star Trek: The Next Generation” star Wil Wheaton is a recurring guest star on “The Big Bang Theory.” He made his first appearance on the series in 2009 during Season 3, episode 5, and has gone on to appear in a dozen more episodes, including the 200th episode.
Danica McKellar (Season 3, episode 12)
“The Wonder Years” alum plays a woman named Abby who hangs out with Raj and Sheldon at a university mixer.
Yeardley Smith (Season 3, episosde 14)
The voice of Lisa Simpson on “The Simpsons” made a cameo on “The Big Bang Theory” as an employment office employee named Sandy. She faces off against Sheldon, who has his own bizarre ideas about what job he’d be good at.
Stan Lee (Season 3, episode 16)
Comic book writer and producer Stan Lee guest starred as himself in “The Excelsior Acquisition.” He appears to sign autographs at Stuart’s comic book shop.
Judy Greer (Season 3, episode 21)
“Married” and “Archer” star Judy Greer heated up the screen when she guest starred as Dr. Elizabeth Plimpton in “The Plimpton Stimulation.”
Steven Yeun (Season 3, episode 22)
Before winning people over as Glenn on “The Walking Dead,” actor Steven Yeun made an appearance on “The Big Bang Theory” as a man named Sebastian. He was Sheldon’s roommate before Leonard moved in.
Steve Wozniak (Season 4, episode 2)
Apple co-founder Steve Wozniak guest stars as himself in “The Cruciferous Vegetable Amplification.” He’s a patron at the Cheesecake Factory where Penny works.
George Takei (Season 4, episode 4)
Howard dreams of “Star Trek” alum George Takei in “The Hot Troll Deviation.”
Eliza Dushku (Season 4, episode 7)
“Angel” alum Eliza Dushku plays an FBI agent who must investigate the gang before giving Howard clearance to work on a project for the Defense Department.
Neil deGrasse Tyson (Season 4, episode 7)
Astrophysicist and cosmologist Neil deGrasse Tyson guest stars as himself in “The Apology Insufficiency.” Sheldon confronts him about “demoting” Pluto.
Rick Fox (Season 4, episode 13)
Actor Rick Fox plays Glenn, Bernadette’s ex-boyfriend in “The Love Car Displacement.”
Jessica Walter (Season 4, episode 15)
“Arrested Development” actress Jessica Walter brought the laughs as a Mrs. Latham, a wealthy benefactor who makes the moves on Leonard.
Josh Malina (Season 4, episode 15)
When he’s not acting as the Attorney General David Rosen on “Scandal,” he’s appeared as Cal Tech’s President Siebert in multiple episodes.
Brent Spiner (Season 5, episode 5)
“Star Trek” alum Brent Spiner made a cameo in this Season 5 episode where Leonard attends a party with fellow “Star Trek” alum Wil Wheaton.
Leonard Nimoy (Season 5, episode 20)
The original Spock actor lent his voice to an action figure in “The Transporter Malfunction.” The action figure puts Sheldon on a guilt trip after he trades broken toys with Leonard.
Stephen Hawking (Season 5, episode 21)
Theoretical physicist and cosmologist Stephen Hawking has made numerous cameos as himself. He even plays “Words with Friends” with Sheldon in one episode. He’s set to make an appearance in the 200th episode.
Howie Mandel (Season 6, episode 4)
Howie Mandel appeared in this Season 6 episode where Howard returns from space. Howard thinks the media is waiting for him when he exits the airport, but he doesn’t realize the game show host is behind him.
Regina King (Season 6, episode 12)
“American Crime” and “The Leftovers” actress Regina King has appeared as human resources administrator Janine Davis in multiple episodes. She doesn’t have the best relationship with Sheldon.
Briana Cuoco (Season 6, episode 16)
Kaley Cuoco’s younger sister, Briana, made a guest appearance as a woman named Gretchen in this Valentine’s Day-themed episode.
Bob Newhart (Season 6, episode 22)
Actor Bob Newhart plays Arthur Jeffries — aka Professor Proton. Professor Proton is Sheldon’s childhood hero and has appeared on multiple episodes.
Bill Nye (Season 7, episode 7)
Science educator Bill Nye “The Science Guy” guest starred as himself in “The Proton Displacement.” Sheldon brings him in to make Professor Proton jealous.
Brian Posehn (Season 7, episode 13)
Comedian Brian Posehn has appeared in two episodes of “The Big Bang Theory” as Bert, a colleague of Amy’s who has a crush on her.
Carrie Fisher (Season 7, episode 14)
James Earl Jones makes Sheldon play a prank on “Star Wars” actress Carrie Fisher in “The Convension Conundrum.”
James Earl Jones (Season 7, episode 14)
Sheldon runs into James Earl Jones and has a wild night out with him.
Casper Smart (Season 7, episode 23)
Jennifer Lopez’s boyfriend, actor and dancer Casper Smart, made a guest appearance during an episode called “The Gorilla Dissolution.” He plays a character named Travis.
Billy Bob Thornton (Season 8, episode 7)
Actor Billy Bob Thornton guest stars as one of Penny’s clients, Dr. Oliver Lorvis. He puts the moves on Penny when he thinks she’s hitting on him.
Max Adler (Season 8, episode 16)
You may have missed “Glee” alum and “Switched at Birth” star Max Adler in this “Big Bang Theory” episode. Adler played a zombie when Leonard, Amy, Raj and Emily try out an “escape room.”
Nathan Fillion (Season 8, episode 15)
Raj and Leonard run into Nathan Fillion at a restaurant. They take an angry selfie with him in “The Comic Book Store Regeneration.”
Kevin Smith (Season 8, episode 20)
Producer and director Kevin Smith lent his voice to “The Big Bang Theory” during “The Fortification Implementation.” Kevin calls into Wil Wheaton’s podcast interview with Penny.
Max Bennett (Season 8, episode 20)
“Victorious” star Max Bennett made an appearance as Howard’s secret half-brother in “The Fortification Implementation.”
Michael Rapaport (Season 9, episode 6)
Leonard and Sheldon meet up with a man named Kenny Fitzgerald to buy helium for a project in “The Helium Insufficiency.” Kenny is played by “Justified” and “My Name is Earl” alum Michael Rapaport.
Adam Nimoy (Season 9, episode 7)
Director Adam Nimoy, the son of Leonard Nimoy, made a guest appearance as himself in “The Spock Resonance.” He’s introduced to Sheldon through Wil Wheaton, who believes Sheldon would be a great person to interview for a “Star Trek” documentary.
Elon Musk (Season 9, episode 9)
The founder of Tesla Motors made a cameo as himself in “The Platonic Permutation.” Howard volunteers alongside him at a soup kitchen on Thanksgiving.
Jane Kaczmarek (Season 9, episode 12)
“Malcolm in the Middle” alum Jane Kaczmarek guest starred in “The Sales Call Sublimation” as a psychiatrist named Dr. Gallo. Leonard schedules an appointment with Dr. Gallo to get Penny into the office to make a sale.
Adam West (Season 9, episode 17)
“Batman” actor Adam West appears as himself in Thursday night’s 200th episode of “Big Bang Theory.”
"The Big Bang Theory" 200th episode airs on CBS Thursday at 8 p.m. EST.